Quick-acting binding post



Feb. 8, 1955 A. RAUCH 2,701,871

QUICK-ACTING BINDING POST Filed Oct. 1, 1952 2 Sheets-Sheet l INVENTOR.ALEXANDER RAUCH Feb. 8, 1955 A. RAUCH QUICK-ACTING BINDING POST 2Sheets-Sheet 2 Filed Oct. 1, 1952 FIG. 7

FIG. l2

FIG. IO

R m m m ALEXANDER RAUCH United States Patent QUICK-ACTING BINDING POSTAlexander Ranch, Red Bank, N. .1.

Application October 1, 1952, Serial No. 312,676

9 Claims. (Cl. 339-254) (Granted under Title 35, U. S. Code (1952), see.266) The invention described herein may be manufactured and used by orfor the Government for governmental purposes, without the payment to meof any royalty thereon.

This invention relates to quick acting binding posts especially adaptedfor use upon electrical apparatus and instruments, for securing wireleads and the like to circuit terminals. It is an important aim of theinvention to present a binding post which will be effective andefiicient under extreme conditions encountered in field operations whereinstruments or apparatus are set up in situations exposed to shock,dust, mud and dirt of various kinds, and temperature extremes. It istherefore a further aim of this invention to otter a construction in anautomatic-grip or clamping post, the function of which will not beeasily impaired in the presence of mud, sand and the like. A further aimis to construct the post in a form which will be easily operablemanually for the rapid connection and release of electrical conductorsserving as leads for electrical energy supplied to or from electricalapparatus.

The present device has been developed with the object of overcoming manyobjections which have been raised to prior binding posts of variouskinds. These prior binding posts have been in three principal classes,viz: (a) the screw-down cap or clamp screw form; (b) the finger-pressedcap spring-grip type, and (c) the fingerpulled spring pressed cap type.

In many of these, transverse apertures are provided to receive the wire,requiring a needle-threading operation in placing the wire. Theclamp-screw type, involves the deformation of the wire at the point ofimpingement of the screw, with increased liability of breakage of thewire under moderate movement or vibration. Many of the screw cap typeinvolve damaging shear engagement of the wire, in addition toneedle-threading and liability of loosening of the screw cap by wiremovements; the danger of deformation of the wire is increased, andcareless manipulation of the cap or screw causes many circuit failures.Both the clamp screw and screw cap types are subject to impairment byjamming of threads by wire or dirt, and crossed threads. They aredilficult to manipulate in confined spaces, and involve excessiveliability of shock to workers and shorts of circuits by tools applied inservicing apparatus.

The automatic spring-actuated finger-released devices have involved theneedle-threading wire placement in many instances, and have alsoinvolved objectionable shear engagement of the wire to hold it. Toeliminate needle-threading, some finger-pressed cap devices have beenprovided with lateral slots permitting a wire end to be inserted bylateral movement of the wire thereinto when finger-pressed to open theslot, but these devices have retained some highly objectionablefeatures, such as the shear grip, space between the grip surfaces toosmall, or surfaces of the grip faces too small, or other shortcomings.

In addition to overcoming the foregoing disadvantages it is an importantaim of the present invention to construct a finger-pressed release typeof binding post which when mounted will withstand severe lateralstresses, such as might be incident to collisions with heavy objects, orblows of tools, or force communicated by a wire held by the device. Inthis connection it is desired to adapt the post to permit wind-around ofthe gripped wire to relieve stress and strain of the gripped part.

A specific aim of the invention is to present a novel construction inthe wire-engaging clamp elements, to the Patented Feb. 8, 1955 end thata wire will be securely held with a minimum liability of casualdisengagement, as well as avoiding liability of damage to the conductorso engaged. It is a related object in this connection to give aneffective assembly of such parts, which may be easily manufactured andassembled with a minimum of difiiculty to present a strong binding postliable in a minimum degree to derangement or damage by rough usage, suchas encountered in military or other field operations.

Another aim of the invention is to originate a post which may be easilymounted upon instrument panels or chassis cases and at the same timewill seal the panels or cases against ingress of water through themounting apertures through which the post is inserted.

It is also an object to present a post having the above advantages whichwill permit ready attachment of a test clip to either the external orinner end of the post. It is further advantage of the invention that itmay be mounted and used in conformity with customary practices in thesetting up of electrical apparatus.

An important purpose of the invention is to present a constructionwherein a complete closure is presented in one of its forms, adapted toprevent access of detritus to the interior of the device, or in thespace in which parts of the device must move.

Additional objects, advantages and features of invention reside in theconstruction, arrangement and combination of parts involved in theembodiment of the invention, as described in the following specificationand accompanying drawings (Figures 4 to 12 being four times actualsize), wherein:

Figure 1 is an elevational view of a post embodying my invention, butunmounted;

Figure 2 is a top view of the assembled post;

Figure 3 is a perspective view of the device mounted on a typicalchassis;

Figure 4 is a fragmentary section of the base portion of the postmounted on the wall of a chassis;

Figure 5 is a section on the line 55 of Figure 2;

Figure 6 is a plan of the grip washer forming the lower jaw element ofthe device;

Figure 7 is an axial section of the upper part of a post of modifiedconstruction;

Figure 8 is a plan of the jaw washer for the last-named modification;

Figure 9 is an axial section of a second modified construction of theinvention;

Figure 10 is a similar view of a third modification;

Figure 11 is a bottom view of the third modification;

Figure 12 is a view similar to Figure 10 of a fourth modification.

Referring to the drawings, there is illustrated a binding postcomprising body part 11, the lower or base portion of which is a simplethreaded shank 12 adapted to receive therearound washers and assembly ormounting at 28, as will be more particularly referred to. The shank hasa hexagonal bolt head 13 thereon, from the center of which there springa coaxial stud 14 of reduced diameter, the upper end of which is formedwith a tenon 15 of further reduced diameter, around which is fitted anupper jaw or grip in the form of a thick washer 16, the extremities ofthe tenon being flared and turned over the washer to retain the samerigidly and permanently in place. The grip 16 is of hardened stainlesssteel knurled on its under face.

Surrounding the stud 14 and spaced therefrom there is an annular wall 17of less than one-half the height of the stud 14, forming a recess 18 andseat for a helical spring 19 fitted loosely around the stud 14, thespring affording a yielding support to a finger-released substantiallytubular cylindrical presser or clamping head 20, or cap, fittedslidingly around the stud 14 and wall 17. The presser head 20 comprisesa substantially cylindrical tube or sleeve, and midway of its height isformed with a horizontal wall or shelf 21' therewith centrally aperturedto fit slidingly around the stud 14. A lower clamping member or grip 22is snugly fitted in the presser head sleeve over the wall 21, this gripbeing in the form of a thin hardened non-corrosive metal washer, knurledon its upper face and receiving the stud 14 slidable therethrough. Byreason of the protractile action of the spring 19 against the wall orshelf 21, the presser head is pressed outwardly so as to tend to holdthe lower grip 22 forcibly against the upper grip 16. A small distance(say, one-sixteenth inch) above the grip 22 a horizontal perimetralwire-receiving slot 23 is formed in the head 20, extendingcircumferentially over an angle of approximately 180 with respect to theaxis of the post, and at each end of this slot the lower edge thereof isrecessed as at 24, so that it extends downwardly slightly below the topface of the grip 22. The upper end of the presser head 20 is rabbettedon the inner side, so that an outer thin wall portion remains. Setwithin the rabbet there is a closing disc 25, and the upper extreme endportion of the thin wall part of the head is spun over this disc toretain the same permanently. The disc 25 serves also as a push plate,against which the finger of the user may engage to depress the pressercap 2%).

The device so described may be mounted in panels or upon chassis casingsin a conventional manner, utiiizing the shank cured by conventionalwashers and nuts, as is familiar in the art.

It should be appreciated that in addition to the strength of the stud14, the device described is adapted to resist comparatively severelateral shocks and stresses applied to the upper part of the device whenmounted, the upstanding wall 17 and apron portion 21 (the lattercornprising the external cylindrical wall of the presser head below thewall or shelf 21) will coact to withstand pressures against the sides ofthe upper parts of the post assembly.

To insure the preservation of circuit elements or other devices enclosedwithin a chassis from damage by water gaining access through theapertures receiving the shank 12, there is shown an improved form of thepost body and cooperating washers by which such. apertures areeffectively sealed by conventional mounting or fastening devices. Thismeans consists in the forming of a concentric groove 26 semicircular incross section in the underface of the bolt head 13, closely around theshank 12, and a soft rubber washer or gasket ring 27 is provided,circular in cross section, fitted around the shank and of a size smallenough in cross section to permit accommodation of the whole deformedwasher within the groove 26 when the head 13 is pressed against thesurface through which the shank 12 is inserted. In one manner of use ofthe device the shank 12 may be inserted through a panel or chassis plateand the latter clamped against the head 13 by means of a lock-washer andnut shown at 28. For use on metallic plates and chassis casings where itis desired to insulate the post, a special washer 29 is provided of asuitable insulating material and this is formed with an annular groove30 in its underside semicircular in cross section and approximating thetransverse size of the groove 26 before described, a central portion ofv the washer being extended axially as a boss at 31, and a soft rubberwasher 32 circular in cross section is fitted around the extension 31 inthe groove 30, and having a cross-sectional dimension such as willpermit the accommodation of the whole washer within the groove 30 whenthe extension 31 of the washer is inserted through a corresponding holein a plate, and the washer 29 pressed toward the plate until the outeredge of the groove 30 engages the plate. A simple annular insulatorwasher 33 is provided, for location at the opposite side of such plate,so that the washers and nut at 28 may clamp the plate between thewashers 33 and 29 as shown in Figure 4.

It will be noted that the extremity of the shank 12 is formed with areduced neck part 35 and a terminal small head 36 well adapted to permitsoldering of conductor wire thereto or to receive the spring-pressedjaws of a test clip. The presser head 20 is likewise adapted to receivea test clip with one jaw inserted in the slot 23 and the other engagedagainst the top of the disc 25 and the top edge of the presser wall.

It is also important to note that this invention has been so constructedthat the device may be manufactured in an extremely small size, thedrawings representing it in this application being several times theactual size throughout the views illustrating the several forms of thedevice, excepting Figures 1, 2, and 3.

In Figure 7 there is shown a modification of the device especiallysuited to mounting the post as an insulated terminal. In this instancethe integral bolt head 13 and enlarged shank 12 are omitted, the body ofthe post com- 12 as a mounting bolt and conductor seprising acylindrical stud 37 with an integral top grip head 8 thereoncorresponding to the shank 14 and grip washer 16. These comprise theprincipal body parts of the post. A shank 39 of slightly reduced size isextended coaxially from the lower end of the stud 37 and provided withwashers and nuts for securement against the face of a panel or chassiswall through which the shank is inserted, and having a tip head 36'similar to the one 36 before mentioned. In place of the bolt head 13 andcase wall 17, a separate cuplike case base 40 is provided formed of arigid insulation material which may comprise hard rubber or one of thesynthetic resins of suitable properties. This base 40 is enlarged at thebottom so as to fit against the face of the panel or chassis, receivingthe shank 39 snugly therethrough. It is formed with an integral caseWall portion 41 similar in form to the case wall portion 17 on the postbody 11; this may be also formed with the concentric annular groove 26in its underface to accommodate a soft rubber ring 27 as in the case ofthe first described form of the device. An insulation washer 42 having aboss thereon to fit in an aperture of a chassis wall 43 or the like isprovided to be opposed to the base 40 when the device is mounted on achassis wall or plate. The upper portion of the device may be the sameas that first described in all respects, but in the present instancethere is shown a modification of the mounting of the lower grip, shownat 43. In this instance the presser head is generally in the same formas the cylindrical part of the presser 2i) first described, but thehorizontal wall 21 is omitted, and in its place a tongue 44 is struckinward in the side of the presser to engage under the grip washer 43opposite the slot 23, which is of the same shape as that firstdescribed. A rib 45 is pressed in the opposite side of the presser head,extending vertically parallel to the stud 37, shaped to fit slidably avertical groove 46 in the base piece 40 so as to hold the presserreciprocally against rotation. The rib 45 stops at the lower side of thegrip washer 43, serving as a support for the latter, and in addition anaperture 47 is formed immediately thereover in the wall of the presser,so as to receive a radial tongue 48 formed integrally on the grip washer43. The upper end of the presser may be closed in any suitable way, as,for instance, in the same manner described in connection with thepresser 20 of Figure 1. The tongue 48 and aperture 47 may be omittedwith further economy, the drive fit of the washer in the presser beingthen depended on to sustain the thrust of the spring.

In Figure 9 there is shown a further modification of the device, inwhich the possibility of leaving the assembly open below the presserhead is indicated, and an improved mounting for the lower grip isindicated, permitting the presser head to be formed from simple tubularstock, which is true of the presser head of Figure 7 also. Also, theupper grip head 50 is formed integrally with the stud 51, these partscorresponding to those 14 and 16 first described. The stud is formedseparately from the bolt head and shank 13 and 12 and secured on thehead by any conventional means, the lower end of the stud being in thisinstance tenoned, cupped and set in a suitable recess in the top of thehead 13' where it may be secured by driving into the head 13, spreadingthe tenon, or otherwise. The presser head is greatly shortened in thisinstance, the skirt portion 21 of the first described form being omittedfor the most part, and the lower grip 52 is formed as a simple washer,having a pressed fit into the presser head 20a from above and supportedat its lower side by a suitable number of instruck tongues 53. The lowergrip may be a simple separate washer, or as shown may have a tongue 54extended therefrom through the apertured wall of the presser headimmediately under the slot 23. The upper end of the presser head may beclosed in the same manner as in the presser head 20 first described.

In Figures 10 and 11 there is shown a further modification of theinvention involving a considerable further simplification and furtherreduction in size. In this instance the shank 12a and bolt head 13:: maybe identical with the shank and head 12 and 13 of Figures 1 and 2, andfrom the head 13a there is extended upwardly an integral or attachedstud 56 of greatly reduced length, upon the upper end of which there issecured an upper grip 16', identical with the one 16 first described andsecured in a like manner, the upper end of the stud being tenoned andupset within a circular recess 57 in the top face of the grip 16. Thepresser head 20b in this from of the invention is a simple shortcylinder or sleeve adapted to be produced from stock tube material,closed at the upper end by a disc 58 pressed thereinto and having theend of the cylinder upset thereover. A central circular boss 59 ispressed downwardly in this disc to afford a seat for the upper end of aprotractile helical spring 60 within the presser head, the lower end ofthe spring being fitted in the recess 57 so as to hold the presser headat the upper limit of its movement. This movement is limited by a lowergrip 61, which is a suitable hardened non-corrosive metal washer knurledon its top side and having opposite radial tongues 62 set in notches 63in the lower edge of the presser head, the edge portions 64 of thepresser head between the notches being upset to retain the disc inplace. The space between the bolt head and presser around-the stud 56 inthis device is entirely clear, permitting the presser to be depressedsufiiciently for the slot 23 to open below the grip 16' to receive awire, or the like, with a minimum of friction and reduced liability ofpacking of dirt between sliding parts. The spring is also more securelyinclosed.

In the assembly of the device of Figure 10, the parts being formed andready for assembly, the lower grip 61 may be pressed and secured in thelower end of the presser sleeve 20* and the lower grip 61 set around thestud 56. The head 16' is then put in place on the stud and the end ofthe tenon of the stud upset to hold it permanently; the spring 60 isthen put in position and the disc 58 set thereover in the upper end ofthe presser 20 after which the top edge of the latter is upset over thedisc to complete the permanent assembly.

In Figure 12 a further modification is shown in which the body of thepost comprises parts corresponding to those last described in Figuresand 11, and have the same reference characters applied with the additionof a prime. The upper grip 16" however, is formed as a stamping in theform of a cup having a cylindrical wall extending upward a proper heightto close the slot in the presser 200 of this device, and the tenon 65 onthe stud is shortened and extended through the bottom of this cup andupset thereover to hold it rigidly in place. The presser 20c also inthis case, is a stamping in the form of an inverted cup, the wall 66 ofwhich is cylindrical and the top 67 of which is integral with the wall66. The lower grip 61 of this device is of the same form as the grip 61of Figure 10, the lower edge of the wall 66 of the presser cup beingnotched in the same manner as the lower edge of the wall of thesleeve-like presser 20b and secured upon the grip 61 by upsetting as at64'. The cup-shaped upper grip 16" thus affords a deep recess withinwhich the spring 60' may be accommodated as shown, and permits theheight of this form of the terminal to be further reduced.

In the assembly of the device of Figure 12, the body of the post and therelated parts having been formed, the grip 61' is laid temporarilyaround the stud S6 and the grip 16" then secured permanently in place byupsetting the tenon 65. The spring 60 is then set over the upper grip,being centered by the upset end of the stud over the grip 16". Thepresser 66 in its cupshape is then inverted over the spring and presseddownward sufliciently to receive the lower grip 61, which is then raisedand pushed into the opening in the cup, after which the bottom edge ofthe presser is upset to retain the lower grip, completing the assemblyof the device. The fastenings and mountings by which the device ismounted on a panel or chassis may conformto those indicated for thefirst described forms of the device, as found best adapted to particularuses contemplated.

It is notable that the forms of the invention in Figures 9, 10 and 11,do not require the presser to be oriented in relation to the body andstud of the post for proper gripping of a wire, but the presser may beturned to the position most convenient at the moment for placing thewire. When a predetermined position is desired, a keyed shaft andinsulator may be provided. A short lead from any direction may thus bereadily accommodated, obviating the need for providing loops of slackwire to enable the bared end to be properly engaged by the device. Italso eliminates the need to orient the post when attaching it to a panelor chassis.

In all the forms of the invention shown and described it will be notedthat the top grids 16, 16', 16", 38 and 50 are of a dimensionlongitudinally of the vertical axis of the devices sufiicient to keepthe slot 23 closed when presser head is at the upper limit of itsmovement, and there is a reasonably close fit of the presser head aroundthis upper grip so that access of dirt over the latter is prevented whenthe device is not in use. It will also be observed that access to thespace between the upper grip and the lower grip in all forms of thisdevice will be substantially closed when a wire or the like is grippedin the device, the form of the slot 23 being such that an engaged wireis positioned near the two extremities of the slot and will be snuglylaid across the grips throughout the engaged portion of such wire, sothat the space between the grips inwardly of the wire opposite the slot23 is closed off.

The longitudinal dimension of the upper parts of the devices of Figures10 and 12 is reduced substantially and owing to the open nature of thespace between the head 13:: and the presser head, impedance of releaseaction of the device by interposed dirt or other material is greatlyminimized.

The reduced size enhances the use of the article in confined spaces, andalso minimizes liability of breakage of the binding post by impact ofrelatively moving bodies, and accidental shorts, as well as economizingthe use of critical materials, the metals most desirable for use in theprincipal parts being in short supplv.

In the production of the several forms of the device the bottom grip maybe secured in the sleeve of the presser head by staking in accordancewith customary practice where available, and in Figure 12, the head 16"may be formed integrally with the stud 56, if desired, in which eventthe complete device would consist of four pieces.

It will be understood that modifications and rearrangements of the partsdisclosed may be made without departing from the spirit of the inventionas hereinafter claimed, including the combination of parts of one viewwith those of another, as may be found expedient and beneficial.

There is a peculiar cooperation between the axial stud 14 and the like,on the one hand, and the wall 17 and skirt 21 and the like on the otherhand, as illustrated in the devices of Figures 1 to 7, consisting in thefact that in this invention it has been made possible to utilize aspring-grip device having a lateral opening to receive a wire end or thelike, and at the same time avoid eccentric, peculiar or diflicultlymanufactured forms, peculiar or excessive machine operations, expensivespecial tools and/or multiplicity of operations or difiicult operations.To this end the invention utilizes the area within the cylindricalpresser 20 and the like only at one side of the simple stud 14 or thecorresponding part in Figures 1 to 7, so that in many instances a singleoperation in a conventional screw machine with appropriate tool form maybe utilized to produce the body of the post in quantity, and the pressermay be formed from stock drawn tube by operations corresponding to thoseheretofore used in parts of some prior device in which more complicatedforms are involved.

In utilizing grip surfaces extending only radially from one side of asubstantially rectilinear, and at least a symmetrical post body, ittherefore becomes desirable to use a body in which the stud part is ofsmall diameter, so that good broad radial areas of grip faces may bemade effective in the opposed grip or jaw elements. Having considerationfor the scale of the drawings in this application, heretofore stated, itwill be appreciated that the stud element of Figures 1 to 7 has in eachinstance been reduced so that it might be considered rather weak if itstood alone, but with the supporting relation of the wall 17, orcorresponding part, and the skirt 21, liability of failure of the deviceunder quite severe blows or lateral pressures, is largely reduced, sothat the device is rugged and highly desirable for the character ofservice indicated hereinbefore.

I claim:

1. An electrical terminal binding post having a base, means to mount thesame, an upstanding stud of small diameter fixed with the base, apresser head coaxially reciprocable thereon and including a sleevespaced around the stud, an upper grip body of much greater diameter thanand fixed on the upper end of the stud, diametrically coextensive withthe interior of and slidingly fitted to said sleeve within the presserhead, said upper grip body having a lower grip face extending from saidsleeve inwardly to said stud, said presser head including a lowerwasher-like grip fixed in the presser head under the upper grip body andreceiving the stud slidingly therethrough, and a compression springengaged between the presser head and said base to hold the presser headat the upper limit of its movement yieldable to manual pressure upon thepresser head, said presser head having a normal released position withsaid lower grip against said upper grip body, and having a horizontalslot in one side above said lower grip and below the top of said uppergrip body, said upper grip body having a vertical dimension greater thanthe vertical dimension of the major medial portion of the slot andpositioned so that the slot is closed by said upper grip body when thepresser head is in said normal position, said slot having opposite endparts extending below the top face of said lower grip so as to lie belowa wire and the like engaged by said lower grip, a chord drawn across thedistal end edges of said slot lying at least close to the periphery ofsaid stud, said presser head being depressible to present said slotbelow said upper grip body a distance sufficient to permit lateralmovement of a wire and the like through the space between the lower sideof the slot and tllie said upper grip body throughout the length of thes ot.

2. The structure of claim 1 wherein the stud is tenoned at its upper endand inserted through the upper grip body, said upper grip securedthereon to hold said upper grip body permanently fixed on the studwithin the presser head, said sleeve of said presser head being open atits upper end initially to receive the upper grip body at leasttherethrough initially and for work in securing the upper grip body onthe stud, and a closure push plate fixed in the upper end of the sleeve.

3. The structure of claim 1 wherein said spring is located between saidbase and lower grip, said base having an upstanding substantiallycylindrical case wall within the presser head, and said presser head hasan apron closely surrounding the upstanding wall as a closure for thespace within said case wall, and around said spring, and extendinglongitudinally beside the case wall a substantial distance, so thatlateral bending of the stud will cause the apron to engage against theside of the wall at the side of incidence of lateral force acting on thepresser head and said wall and apron together will resist lateraldisplacement of the upper part of the terminal when mounted, and opposebending strain of the stud.

4. In a terminal of the character described, a post body adapted to besecured upon a support and comprising a stud, a lower grip slidablelongitudinally on said stud, a fixed top grip on the extremity of thestud over said lower grip to coact with the latter when raisedtheretoward, a presser member of substantially tubular form having thelower grip fixed in a lower part thereof, and a protractile springcoacting between the post body and the presser to hold the latter at theupper limit of its movement limited by said upper grip and yieldable tofinger pressure thereon to move the lower grip from the upper one, saidpresser having a horizontal slot in one side thereof extending over anarc the chord of which extends at least closely without said stud, saidpresser having an initial disengaged and closed position at the upperlimit of its movement around the upper grip, said upper grip having anouter face closely against the inner face of the presser and extendingover the whole length of said slot to close the same when the presser isat the upper limit of its movement on said stud, said presser having anopen depressed position to lower said lower grip from the upper grip andwith said slot aligned with the space between the grips, said slothaving a central part above the lower grip and extremities extending adistance horizontally below the top face of the lower grip.

5. The structure of claim 4 wherein said lower grip consists of a washershaped plate having longitudinally locked coengagement with the presserhead at one side and a pressed fit within the head, the locked part ofthe lower grip being midway of the length of said slot.

6. The structure of claim 3 wherein a vertical groove is formed in theouter side of the said upstanding wall, and an interior rib is pressedin one side of the apron fitted slidingly in the groove, said ribstopping short at the lower side of said lower grip as a stop andsupport for the latter.

7. The structure of claim 4, wherein said lower grip is a thinwasher-shaped disc of hardened corrosion-resistant metal having at leastone integral radial ear, said presser member being notched at its loweredge to receive such ear, said grip being fitted in the lower end of thepresser with said ear set in said notch, and the lower edge of thepresser upset upon the grip to retain the same.

8. The structure of claim 7 wherein the said upper grip is a discintegral with said stud, said terminal including a base member receivingan extension of the stud, whereby said lower grip may be introduced onthe stud before mounting, and assembled on the presser.

9. The structure of claim 8 wherein said presser is an invertedcylindrical cup-shaped member, said spring being positioned over saidupper grip and confined by the cup.

References Cited in the file of this patent UNITED STATES PATENTS1,594,456 Conway Aug. 3, 1926 1,660,807 Norgren Feb. 28, 1928 1,746,639Dunzweiler Feb. 11, 1930 2,293,719 Eby g Aug. 25, 1942 2,567,510Drescher Sept. 11, 1951 2,605,315 Hargett July 29, 1952 FOREIGN PATENTS93,547 Austria July 10, 1923

